1. Field of the Invention
The present invention relates to denture rebases.
2. Description of the Related Art
Acrylic, polysulfone or polycarbonate dentures are typically used in dental treatment for the aged and those who have lost their teeth. In general, however, ridge resorption is often remarkable in cases with dentures. In such cases, the alveolar bone will often xe2x80x9ccave inxe2x80x9d as the oral mucous membrane that helps to cushion the teeth becomes poor and also as the jawbone is resorbed. Accordingly, over time, the fit of even well-made dentures will progressively become worse.
In cases where the denture has failed to fit well within the oral cavity, a denture rebase is generally applied. A denture rebase reconstitutes the surface of the denture that faces the oral mucous membrane; and the thus-reconstructed denture fits better in the mouth. These denture rebases are used as follows: an un-polymerized and un-cured denture rebase (i.e., one that is pasty) is applied to the surface of the ill-fitting denture that faces the oral mucous membrane, then the denture, together with the applied rebase on its surface is returned to the oral cavity of the patient, and the upper and lower teeth of the patient are made to occlude such that the denture is in good contact with the oral mucous membrane and such that the rebase on the denture is impressed with the surface profile of the oral mucous membrane, and thereafter the rebase is polymerized and cured. In this treatment, the rebase can be directly polymerized and cured while it is still in the oral cavity or, alternatively, the rebase may be taken out after having been once impressed with the surface profile of the oral mucous membrane, and then polymerized and cured outside the oral cavity.
However, compared to the dentures themselves, conventional denture rebases are problematic in that they are readily discolored, they absorb odorous substances and water, and they are easily contaminated and stained if they remain in the oral cavity for a long time. In addition, the care of such dentures is often more difficult for aged persons, and dentures relined with such conventional rebases are easily contaminated and stained with use, which adds to the worsening of the dental condition of the patient. Another problem with conventional rebases is that they are often painful to the patients who undergo dental treatment with them. This is because of the irritation caused to the oral mucous membrane during contact with the rebase before polymerization.
To prevent denture rebases from being contaminated and stained, fluorine-containing dental materials have been proposed. Such materials typically contain (meth)acrylate monomers having fluorine atoms. For example, Japanese Patent Laid-Open No. 33110/1987 discloses a dental composition containing an acrylate polymer having a fluorine atom in its xcex1-position. The composition gives a dental material having high mechanical strength. However, this dental material is undesirably subject to discoloration, its staining resistance is not satisfactory, and it absorbs odorous substances and water while in the oral cavity. In addition, even though the dental material has high mechanical strength, it is not tough and its cured product is hard and brittle.
In Dental Materials and Appliances, Vol. 9, No. 2, pp. 257-264 (1990), a composition for soft denture rebases is disclosed, which contains, as the polymer ingredient of fluororubber, a vinylidene fluoride-hexafluoropropylene copolymer or a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, and, as the monomer ingredient, a fluoro(meth)acrylate having 2 to 5 side-chain carbons. As compared with conventional soft rebases, those prepared by polymerizing and curing the composition disclosed therein are better since they absorb a reduced amount of water and release a reduced amount of the constituent monomer; but they are still unsatisfactory since they are readily discolored and stained, and they absorb odors in the mouth.
In Dental Materials and Appliances, Vol. 2, No. 1, pp. 50-57 (1983), a dental resin is disclosed that contains, as the polymer component, polymethyl methacrylate and, as the monomer component, 2,2,2-trifluoroethyl methacrylate. The primary advantage of this resin composition is that the amount of protein that adheres to it is reduced in some degree. However, its effect is not satisfactory and, in addition, the dental resin is easily discolored and stained, and it absorbs water and odors while used in the mouth.
In the conventional methods mentioned above, it is difficult to obtain denture rebases having satisfactory discoloration and staining resistance, odor absorption resistance and water absorption resistance. In addition, the polymerized and cured products of the conventional materials noted above are undesirably brittle though being hard. Moreover, still another problem is that the convention denture rebases irritate the oral mucous membrane when, prior to their being polymerized, they are kept in contact with the oral mucous membrane while being impressed with the surface profile thereof.
Accordingly, conventional denture rebases have the serious problem in that they are easily contaminated and stained as compared with the dentures themselves. Dental materials containing a fluoro(meth)acrylate have been used, but which are still defective in that their contamination and staining resistance is not satisfactory, and they become brittle after curing.
Accordingly, one object of the invention is to provide denture rebases having good contamination and staining resistance.
Another object of the invention is to provide denture rebases that remain tough after being cured.
Another object of the invention is to provide denture rebases that do not irritate the oral mucous membrane while being impressed with the surface profile of the oral mucous membrane.
Another object of the invention is to provide denture rebases that do not cause pain to the patients who undergo dental treatment with them.
These and other objects have been attained by the present invention, the first embodiment of which provides a denture rebase that includes:
(a) an acrylic resin;
(b) a fluoro(meth)acrylate having the formula (I):
CH2xe2x95x90C(R1)COOxe2x80x94R2xe2x80x94Rfxe2x80x83xe2x80x83(I)
wherein R1 represents a hydrogen atom or a methyl group; R2 represents an alkylene group; Rf represents a perfluoro alkyl group; R2+Rf has 4 to 10 carbon atoms in total, and wherein at least 50% of all atoms bonded to said carbon atoms constituting R2+Rf are fluorine atoms;
(c) a polyfinctional (meth)acrylate; and
(d) a polymerization initiator.
Another embodiment of the invention provides a dental rebase, that includes the cured reaction product of the above-noted (a), (b), (c) and (d).
Another embodiment of the invention provides a method of making the denture rebase, that includes combining the above-noted (a), (b), (c) and (d).
Another embodiment of the invention provides a method rebasing a denture. that includes applying to a surface of a denture the above denture rebase composition.
Another embodiment of the invention provides a two-package powder/liquid composition, which includes:
a powder package, including:
(a) an acrylic resin powder, and
(dxe2x80x2) a peroxide; and
a liquid package, including:
(b) a fluoro(meth)acrylate having the formula (I):
CH2xe2x95x90C(R1)COOxe2x80x94R2xe2x80x94Rfxe2x80x83xe2x80x83(I)
xe2x80x83wherein R1 represents a hydrogen atom or a methyl group; R2 represents an alkylene group; Rf represents a perfluoro alkyl group; R2+Rf has 4 to 10 carbon atoms in total, and wherein at least 50% of all atoms bonded to said carbon atoms constituting R2+Rf are fluorine atoms,
(c) a polyftnctional (meth)acrylate, and
(dxe2x80x3) a tertiary amine;
xe2x80x83wherein when (dxe2x80x2) and (dxe2x80x3) are combined, a polymerization initiator (d), is formed.
Another embodiment of the invention provides a method for making a dental rebase, that includes combining the above powder and liquid packages.